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		<title>three.js webgl - teapot buffer geometry</title>
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		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - the Utah Teapot<br />
			from <a href="https://www.udacity.com/course/interactive-3d-graphics--cs291" target="_blank" rel="noopener">Udacity Interactive 3D Graphics</a>
		</div>

		<script type="module">

			import * as THREE from '../build/three.module.js';

			import { GUI } from './jsm/libs/dat.gui.module.js';

			import { OrbitControls } from './jsm/controls/OrbitControls.js';
			import { TeapotGeometry } from './jsm/geometries/TeapotGeometry.js';

			let camera, scene, renderer;
			let cameraControls;
			let effectController;
			const teapotSize = 400;
			let ambientLight, light;

			let tess = - 1;	// force initialization
			let bBottom;
			let bLid;
			let bBody;
			let bFitLid;
			let bNonBlinn;
			let shading;
			let wireMaterial, flatMaterial, gouraudMaterial, phongMaterial, texturedMaterial, reflectiveMaterial;

			let teapot, textureCube;

			// allocate these just once
			const diffuseColor = new THREE.Color();
			const specularColor = new THREE.Color();

			init();
			render();

			function init() {

				const container = document.createElement( 'div' );
				document.body.appendChild( container );

				const canvasWidth = window.innerWidth;
				const canvasHeight = window.innerHeight;

				// CAMERA
				camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 80000 );
				camera.position.set( - 600, 550, 1300 );

				// LIGHTS
				ambientLight = new THREE.AmbientLight( 0x333333 );	// 0.2

				light = new THREE.DirectionalLight( 0xFFFFFF, 1.0 );
				// direction is set in GUI

				// RENDERER
				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( canvasWidth, canvasHeight );
				renderer.outputEncoding = THREE.sRGBEncoding;
				container.appendChild( renderer.domElement );

				// EVENTS
				window.addEventListener( 'resize', onWindowResize );

				// CONTROLS
				cameraControls = new OrbitControls( camera, renderer.domElement );
				cameraControls.addEventListener( 'change', render );

				// TEXTURE MAP
				const textureMap = new THREE.TextureLoader().load( 'textures/uv_grid_opengl.jpg' );
				textureMap.wrapS = textureMap.wrapT = THREE.RepeatWrapping;
				textureMap.anisotropy = 16;
				textureMap.encoding = THREE.sRGBEncoding;

				// REFLECTION MAP
				const path = "textures/cube/pisa/";
				const urls = [
					path + "px.png", path + "nx.png",
					path + "py.png", path + "ny.png",
					path + "pz.png", path + "nz.png"
				];

				textureCube = new THREE.CubeTextureLoader().load( urls );
				textureCube.encoding = THREE.sRGBEncoding;

				// MATERIALS
				const materialColor = new THREE.Color();
				materialColor.setRGB( 1.0, 1.0, 1.0 );

				wireMaterial = new THREE.MeshBasicMaterial( { color: 0xFFFFFF, wireframe: true } );

				flatMaterial = new THREE.MeshPhongMaterial( { color: materialColor, specular: 0x000000, flatShading: true, side: THREE.DoubleSide } );

				gouraudMaterial = new THREE.MeshLambertMaterial( { color: materialColor, side: THREE.DoubleSide } );

				phongMaterial = new THREE.MeshPhongMaterial( { color: materialColor, side: THREE.DoubleSide } );

				texturedMaterial = new THREE.MeshPhongMaterial( { color: materialColor, map: textureMap, side: THREE.DoubleSide } );

				reflectiveMaterial = new THREE.MeshPhongMaterial( { color: materialColor, envMap: textureCube, side: THREE.DoubleSide } );

				// scene itself
				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0xAAAAAA );

				scene.add( ambientLight );
				scene.add( light );

				// GUI
				setupGui();

			}

			// EVENT HANDLERS

			function onWindowResize() {

				const canvasWidth = window.innerWidth;
				const canvasHeight = window.innerHeight;

				renderer.setSize( canvasWidth, canvasHeight );

				camera.aspect = canvasWidth / canvasHeight;
				camera.updateProjectionMatrix();

				render();

			}

			function setupGui() {

				effectController = {

					shininess: 40.0,
					ka: 0.17,
					kd: 0.51,
					ks: 0.2,
					metallic: true,

					hue:	0.121,
					saturation: 0.73,
					lightness: 0.66,

					lhue:	0.04,
					lsaturation: 0.01,	// non-zero so that fractions will be shown
					llightness: 1.0,

					// bizarrely, if you initialize these with negative numbers, the sliders
					// will not show any decimal places.
					lx: 0.32,
					ly: 0.39,
					lz: 0.7,
					newTess: 15,
					bottom: true,
					lid: true,
					body: true,
					fitLid: false,
					nonblinn: false,
					newShading: "glossy"
				};

				let h;

				const gui = new GUI();

				// material (attributes)

				h = gui.addFolder( "Material control" );

				h.add( effectController, "shininess", 1.0, 400.0, 1.0 ).name( "shininess" ).onChange( render );
				h.add( effectController, "kd", 0.0, 1.0, 0.025 ).name( "diffuse strength" ).onChange( render );
				h.add( effectController, "ks", 0.0, 1.0, 0.025 ).name( "specular strength" ).onChange( render );
				h.add( effectController, "metallic" ).onChange( render );

				// material (color)

				h = gui.addFolder( "Material color" );

				h.add( effectController, "hue", 0.0, 1.0, 0.025 ).name( "hue" ).onChange( render );
				h.add( effectController, "saturation", 0.0, 1.0, 0.025 ).name( "saturation" ).onChange( render );
				h.add( effectController, "lightness", 0.0, 1.0, 0.025 ).name( "lightness" ).onChange( render );

				// light (point)

				h = gui.addFolder( "Lighting" );

				h.add( effectController, "lhue", 0.0, 1.0, 0.025 ).name( "hue" ).onChange( render );
				h.add( effectController, "lsaturation", 0.0, 1.0, 0.025 ).name( "saturation" ).onChange( render );
				h.add( effectController, "llightness", 0.0, 1.0, 0.025 ).name( "lightness" ).onChange( render );
				h.add( effectController, "ka", 0.0, 1.0, 0.025 ).name( "ambient" ).onChange( render );

				// light (directional)

				h = gui.addFolder( "Light direction" );

				h.add( effectController, "lx", - 1.0, 1.0, 0.025 ).name( "x" ).onChange( render );
				h.add( effectController, "ly", - 1.0, 1.0, 0.025 ).name( "y" ).onChange( render );
				h.add( effectController, "lz", - 1.0, 1.0, 0.025 ).name( "z" ).onChange( render );

				h = gui.addFolder( "Tessellation control" );
				h.add( effectController, "newTess", [ 2, 3, 4, 5, 6, 8, 10, 15, 20, 30, 40, 50 ] ).name( "Tessellation Level" ).onChange( render );
				h.add( effectController, "lid" ).name( "display lid" ).onChange( render );
				h.add( effectController, "body" ).name( "display body" ).onChange( render );
				h.add( effectController, "bottom" ).name( "display bottom" ).onChange( render );
				h.add( effectController, "fitLid" ).name( "snug lid" ).onChange( render );
				h.add( effectController, "nonblinn" ).name( "original scale" ).onChange( render );

				// shading

				gui.add( effectController, "newShading", [ "wireframe", "flat", "smooth", "glossy", "textured", "reflective" ] ).name( "Shading" ).onChange( render );

			}


			//

			function render() {

				if ( effectController.newTess !== tess ||
					effectController.bottom !== bBottom ||
					effectController.lid !== bLid ||
					effectController.body !== bBody ||
					effectController.fitLid !== bFitLid ||
					effectController.nonblinn !== bNonBlinn ||
					effectController.newShading !== shading ) {

					tess = effectController.newTess;
					bBottom = effectController.bottom;
					bLid = effectController.lid;
					bBody = effectController.body;
					bFitLid = effectController.fitLid;
					bNonBlinn = effectController.nonblinn;
					shading = effectController.newShading;

					createNewTeapot();

				}

				// We're a bit lazy here. We could check to see if any material attributes changed and update
				// only if they have. But, these calls are cheap enough and this is just a demo.
				phongMaterial.shininess = effectController.shininess;
				texturedMaterial.shininess = effectController.shininess;

				diffuseColor.setHSL( effectController.hue, effectController.saturation, effectController.lightness );
				if ( effectController.metallic ) {

					// make colors match to give a more metallic look
					specularColor.copy( diffuseColor );

				} else {

					// more of a plastic look
					specularColor.setRGB( 1, 1, 1 );

				}

				diffuseColor.multiplyScalar( effectController.kd );
				flatMaterial.color.copy( diffuseColor );
				gouraudMaterial.color.copy( diffuseColor );
				phongMaterial.color.copy( diffuseColor );
				texturedMaterial.color.copy( diffuseColor );

				specularColor.multiplyScalar( effectController.ks );
				phongMaterial.specular.copy( specularColor );
				texturedMaterial.specular.copy( specularColor );

				// Ambient's actually controlled by the light for this demo
				ambientLight.color.setHSL( effectController.hue, effectController.saturation, effectController.lightness * effectController.ka );

				light.position.set( effectController.lx, effectController.ly, effectController.lz );
				light.color.setHSL( effectController.lhue, effectController.lsaturation, effectController.llightness );

				// skybox is rendered separately, so that it is always behind the teapot.
				if ( shading === "reflective" ) {

					scene.background = textureCube;

				} else {

					scene.background = null;

				}

				renderer.render( scene, camera );

			}

			// Whenever the teapot changes, the scene is rebuilt from scratch (not much to it).
			function createNewTeapot() {

				if ( teapot !== undefined ) {

					teapot.geometry.dispose();
					scene.remove( teapot );

				}

				const teapotGeometry = new TeapotGeometry( teapotSize,
					tess,
					effectController.bottom,
					effectController.lid,
					effectController.body,
					effectController.fitLid,
					! effectController.nonblinn );

				teapot = new THREE.Mesh(
					teapotGeometry,
					shading === "wireframe" ? wireMaterial : (
						shading === "flat" ? flatMaterial : (
							shading === "smooth" ? gouraudMaterial : (
								shading === "glossy" ? phongMaterial : (
									shading === "textured" ? texturedMaterial : reflectiveMaterial ) ) ) ) );	// if no match, pick Phong

				scene.add( teapot );

			}

		</script>

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